Set user of a vncserver display

Someone can explain to me what file i must change/create on my xu4 to achieve this?

I tested to add a

 etc/vnc.conf

with no sucess.

I looked inside

/Dietpi/dietpi.txt

and didnt see an option to activate or change the default user.

Some news.

I am trying to follow this (i know it’s for CentOs).

I have found some interesting file in /usr/local/bin and in /usr/bin but nothing like the step 2.2.